Banknotes are sent and swapped so much easier now, to the great delight of notaphilists all over the world. It used to be that you had to go to offices and banks to acquire uncirculated or about "uncirculated bills" to add to your collection. Now catalogues from the US, Germany and France are online.
Collectors' banknotes are not only "uncirculated." They're also "gem", "choice," and "crisp," in that descending order, according to how mint the condition is.